Assessing the Peak Capacity of IMS−IMS Separations of Tryptic Peptide Ions in He at 300 K

Abstract

Two-dimensional ion mobility spectrometry (IMS-IMS) coupled with mass spectrometry is examined as a means of separating mixtures of tryptic peptides (from myoglobin and hemoglobin). In this study, we utilize two distinct drift regions that are identical in that each contains He buffer gas at 300 K. The two-dimensional advantage is realized by changing the structures of the ions. As ions arrive at the end of the first drift region, those of a specified mobility are selected, exposed to energizing collisions, and then introduced into a second drift region. Upon collisional activation, some ions undergo structural transitions, leading to substantial changes in their mobilities; others undergo only slight (or no) mobility changes. Examination of peak positions and shapes for peptides that are separated in the first IMS dimension indicates experimental peak capacities ranging from approximately 60 to 80; the peak shapes and range of changes in mobility that are observed in the second drift region (after activation) indicate a capacity enhancement ranging from a factor of approximately 7 to 17. Thus, experimental (and theoretical) evaluation of the peak capacity of IMS-IMS operated in this fashion indicates that capacities of approximately 480 to 1360 are accessible for peptides. Molecular modeling techniques are used to simulate the range of structural changes that would be expected for tryptic peptide ions and are consistent with the experimental shifts that are observed.

Advanced Multidimensional Separations in Mass Spectrometry: Navigating the Big Data Deluge

“…For example, MS calculations for peak capacity are based on methods developed by Frahm et al , which account for instrument resolving powers and isotope redundancy (78) and utilize typical, rather than optimal parameters for each method (79). For IM, peak capacities are obtained from measured values of different techniques where available (80,81,82), or otherwise calculated from reported resolving powers (83,84). For IM coupled to MS (IM-MS), there is a correlation between size and mass, and so IM-MS data in Figure 2 is scaled by a factor of 0.25 (25% unique space occupancy) to reflect this reduced orthogonality, which is based on experiments conducted in the authors’ laboratory.…”

10years of MS instrumental developments – Impact on LC–MS/MS in clinical chemistry

“…In principle each of these ion mobility devices can be interfaced to a variety of mass spectrometers; TOF analyzers are used most frequently but also combinations with quadrupole and ion trap systems can be found. To extend the possibilities even further an ion mobility cell can be interfaced to other ion mobility cells together with tandem mass spectrometers to produce IMS n -MS m type analyzers [108,109].…”

Peptidomics: The integrated approach of MS, hyphenated techniques and bioinformatics for neuropeptide analysis

“…Another possibility for IMS -IMS is that after the first dimension, energizing collisions change the structural transitions, which alters their behaviour in the second IMS drift field. This way, the two IMS separations are more orthogonal [118].…”